Machining system for aircraft structural components

ABSTRACT

The disclosure relates to a machining system for aircraft structural components, comprising a first frame for mounting a workpiece, and a second frame for mounting a tool pair including an upper tool and a lower tool cooperating therewith. The workpiece is positioned between the upper tool and the lower tool. The second frame is formed to be displaceable at least in a longitudinal direction with respect to a base. The tool pair is held in the second frame such that it is displaceable in a transverse direction which is at an angle to the longitudinal direction. The second frame is held on at least one swivel bearing so that the second frame can be adjustably swiveled together with the tool pair about a swivel axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. 371 ofInternational Patent Application Serial No. PCT/EP2016/059480, entitled“MACHINING SYSTEM FOR AIRCRAFT STRUCTURAL COMPONENTS,” filed Apr. 28,2015, which claims priority from German Patent Application No. DE 102015 106 543.6, filed Apr. 28, 2015, the disclosure of which isincorporated herein by reference.

FIELD OF THE TECHNOLOGY

The disclosure relates to a machining system for aircraft structuralcomponents and a process for machining an aircraft structural componentwith a machining system.

BACKGROUND

U.S. Pat. No. 8,220,134 B2 describes a machining system for aircraftstructural components, in which a riveting unit having an upper tool anda lower tool is arranged in a C-shaped frame. A clamping frame isprovided here for fastening an aircraft structural component and is heldat two ends on a respective tower. The clamping frame is thus verticallydisplaceable and rotatable about a longitudinal axis separately at eachend. The riveting unit in the C-shaped frame is displaceable as a wholealong a horizontal X-axis and the towers are each displaceable in ahorizontal Y-axis perpendicular to the X-axis.

From practice, machining systems are moreover known in which theriveting unit is held in a closed rectangular frame through which theclamping frame reaches. The riveting unit is displaceable in theY-direction within this frame and the entire frame is displaceable inthe X-direction. The towers here are arranged in a stationary manner andare not displaceable relative to a base.

For machining aircraft structural components, it is furthermore known toprovide a riveting tool having an upper and lower tool at one end of amulti-axis robot arm. Such an arrangement is only suitable forcomponents having a limited width.

SUMMARY

It is an object of the disclosure to provide a machining system foraircraft structural components, which enables space-saving machining.

For a machining system described at the outset, this object can beachieved by features described herein. By providing a swivel bearing onthe second frame, it is easily possible to achieve an alignment of theangle of the upper and lower tool with respect to a surface of theworkpiece. In particular, the necessary movement of the workpiece bymeans of the second frame can thus be reduced. Moreover, forparticularly strongly domed workpieces, or for workpieces havingstructures which are inclined relative to the surface, machining whichcannot be achieved with conventional machining systems is enabled.

Within the context of various embodiments, a frame refers to anysupporting and inherently rigid structure on which a component is held.A frame can comprise a plurality of mutually separate sub-components.

Within the context of various embodiments, a longitudinal direction, atransverse direction and optionally a vertical direction are defined,which are each at an angle to one another. Through a movement along theangled directions, it is thus possible to approach a point in space.Within the context of various embodiments, directions can refer tospatially fixed, unalterable directions or axes. In a concreterealization, these directions are often, but not necessarily, spatiallyfixed axes of a Cartesian coordinate system, wherein the axes areorientated at a right angle to one another. In this specific case, thelongitudinal direction is also known as the X-axis, the transversedirection as the Y-axis and the vertical direction as the Z-axis.

A workpiece refers to a component of an aircraft structure which is tobe machined by the machining system. In some embodiments, these arelight metal components of the aircraft, for example fuselage, wing ortailplane parts, which are to be riveted.

A tool pair having an upper tool and a lower tool refers here inparticular to any tool in which the upper tool and the lower tool haveto simultaneously cooperate with the workpiece to achieve machining Thisresults in corresponding demands relating to the displacement paths, themounting and the precision of the positioning of the tool pair.

A machining system according to some embodiments is generally acomputer-controlled system in which the positioning and machiningprocedures take place automatically by means of electric, hydraulic orother motors and/or actuators.

In an embodiment, the tool pair comprises a riveting tool or a combinedtool for drilling and riveting. One of the two, in particular the uppertool, is formed here for supplying a rivet, wherein the other in eachcase, in particular the lower tool, functions as a counter-bearingduring a deformation of the rivet. Corresponding demands are thus madeon the introduction of force into the second frame. A combination of adrilling and riveting tool can be present, as is known in general andfrom the machining systems mentioned at the outset. After approaching amachining position, a hole can firstly be incorporated in the workpieceby means of a drilling tool, after which a rivet is incorporated anddeformed in the hole by means of the combined riveting tool.

A swivel bearing or a swivel movement of the second frame generallyrefers to a movement about the swivel axis on which a linear movementperpendicular to the axis can also be superimposed. It would be possibleto realize such a superimposed movement, for example, if the secondframe were moved via a bearing in a guideway which is not curvedcircularly. In some embodiments, however, the swivel movement takesplace as a simple rotation, wherein the swivel axis is formed as an axisof rotation. Such a rotation can take place via a simple pivot bearingacting as a swivel bearing.

The second frame is generally advantageously held on a base frame viathe swivel bearing, wherein the base frame is displaceable in thelongitudinal direction on a guide. This enables easy and, at the sametime, precise positioning of the tool pair in the longitudinaldirection. In other embodiments, however, the workpiece or the firstframe could also be formed to be displaceable in the longitudinaldirection.

In a particularly stable embodiment of the mounting of the tool pair,the second frame has a supporting structure encompassing the tool pairin a closed manner, wherein the workpiece reaches through an openingsurrounded by the supporting structure. For example, this can be arectangular frame in which the upper tool and the lower tool are held onmutually opposing sides of the frame.

At least one of the two, the upper tool or the lower tool, is generallyadvantageously adjustably displaceable relative to the second frame in atool direction which is at an angle to the transverse direction. Thisenables particularly quick and precise positioning in the transversedirection. In other embodiments, the workpiece or the first frame can beadditionally or alternatively formed to be displaceable in thetransverse direction.

In an embodiment, the first frame comprises two positioning towers. Thepositioning towers can be positioned separately from one another in astationary manner. The workpiece can be held between the positioningtowers, wherein it is optionally movable by means of the positioningtowers. Separate positioning of the positioning towers enables thesystem to be adapted to different sizes of workpiece. The positioningtowers can be stationary in the sense that they are not movable duringthe machining of a workpiece.

The first frame generally advantageously has a first holder and a secondholder, which are arranged at two opposing end regions of the workpiece,wherein the first holder is adjustably displaceable in a verticaldirection which is at an angle to the longitudinal direction and also tothe transverse direction. The angle of the workpiece can thus bepositioned with respect to the tool pair. For further alignment, in anembodiment, the first holder is formed to be adjustably rotatable,wherein the workpiece is rotatable about a workpiece axis through therotation of the first holder. The workpiece axis can extend inparticular approximately along a longest length of the workpiece,whereby the rotation about the workpiece axis is particularlyspace-saving.

The second holder can furthermore also be adjustably displaceable in thevertical direction. Both a first end and a second end of the workpiececan thus be vertically displaced independently of one another, so thatboth an overall height and also an inclination of the workpiece aboutthe transverse direction are adjustable. To compensate a change in thespacing between the holders which occurs during the vertical adjustment,a longitudinal compensation means, for example in the manner of atelescopic guide, can be formed on one of the holders in a known manner.

A clamping frame can be connected to the first holder and to the secondholder, wherein the workpiece can be releasably fastened to the clampingframe and the clamping frame is movable by means of the holders. Thisalso enables precise clamping and positioning of workpieces which arelarger and have substantially any form. In alternative embodiments,however, the workpiece can also be arranged in a self-supporting mannerbetween the holders.

An object of the disclosure is moreover achieved by a process formachining an aircraft structural component with a machining systemaccording to the disclosure, comprising the steps:

-   -   a) clamping a workpiece which has a non-planar surface in the        longitudinal direction, in particular a surface having a dome,        in the first frame and calibrating a tool position relative to        the workpiece;    -   b) approaching a first machining position and machining the        workpiece;    -   c) approaching a second machining position which is different at        least in the longitudinal direction, wherein the second frame is        swiveled about the swivel axis depending on the surface of the        workpiece in order to align the tool direction in its        orientation with respect to the surface of the workpiece; and    -   d) machining the workpiece in the second machining position.

Through the provision of the swivel axis on the second frame, theadaptation of the tool direction or a machining direction whenapproaching the second machining position can take place quickly andeasily. The tool direction here is aligned perpendicularly to thesurface in the machining position. The tool direction refers inparticular to the riveting direction when the tool pair is formed as ariveting tool.

An embodiment provides a machining system for aircraft structuralcomponents, comprising a first frame for mounting a workpiece, and asecond frame for mounting a tool pair comprising an upper tool and alower tool cooperating therewith, wherein the workpiece is positionedbetween the upper tool and the lower tool, wherein the second frame isformed to be displaceable at least in a longitudinal direction withrespect to a base, and wherein the tool pair is held in the second framesuch that it is displaceable in a transverse direction which is at anangle to the longitudinal direction, wherein the second frame is held onat least one swivel bearing so that the second frame can be adjustablyswiveled together with the tool pair about a swivel axis.

In some embodiments, the tool pair comprises a riveting tool or acombined tool for drilling and riveting.

In some embodiments, the second frame is held on a base frame via theswivel bearing, wherein the base frame is displaceable in thelongitudinal direction on a guide.

In some embodiments, the second frame comprises a supporting structureencompassing the tool pair in a closed manner, wherein the workpiecereaches through an opening surrounded by the supporting structure.

In some embodiments, at least one of the two, the upper tool or thelower tool, is adjustably displaceable relative to the second frame in atool direction which is at an angle to the transverse direction.

In some embodiments, the first frame comprises two positioning towerswhich can be positioned in particular separately from one another in astationary manner.

In some embodiments, the first frame has at least a first holder and asecond holder, which are arranged at two opposing end regions of theworkpiece, wherein the first holder is adjustably displaceable in avertical direction which is at an angle to the longitudinal directionand the transverse direction.

In some embodiments, the first holder is adjustably rotatable, whereinthe workpiece is rotatable about a workpiece axis through the rotationof the first holder.

In some embodiments, the second holder is also adjustably displaceablein a vertical direction.

In some embodiments, a clamping frame is connected to the first holderand to the second holder, wherein the workpiece can be releasablyfastened to the clamping frame and the clamping frame is movable bymeans of the holders.

An embodiment provides a method for machining an aircraft structuralcomponent by means of a machining system according to the disclosure,characterized by the steps: clamping a workpiece which has a non-planarsurface in the longitudinal direction, in particular a surface having adome, in the first frame and calibrating a tool position relative to theworkpiece; approaching a first machining position and machining theworkpiece; approaching a second machining position which is different atleast in the longitudinal direction, wherein the second frame isswiveled about the swivel axis depending on the surface of the workpiecein order to align the tool direction in its orientation with respect tothe surface of the workpiece; machining the workpiece in the secondmachining position.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and features of various embodiments are revealed inan exemplary embodiment described below and explained in more detailwith reference to the accompanying drawings. The drawings show:

FIG. 1 a three-dimensional overall view of a machining system accordingto an embodiment;

FIG. 2 a schematic illustration of axes, directions and planes of themachining system of FIG. 1 in the machining position shown in FIG. 1;

FIG. 3 the schematic illustration of FIG. 2 in a second machiningposition; and

FIG. 4 the schematic illustration of FIG. 2 in a third machiningposition.

DETAILED DESCRIPTION

The machining system shown in FIG. 1 comprises a first frame 1, whichcomprises a first positioning tower 2 and a second positioning tower 3.Arranged on each of the positioning towers 2, 3 is a respective holder4, 5, which are displaceable in each case in perpendicular and parallelvertical directions H1, H2 here by means of a controlled drive.

Each of the holders 4, 5 is rotatable about a workpiece axis A, whereinthe orientation of the workpiece axis A depends on the respectiveposition of the holders 4, 5 in the vertical directions H1, H2.

A clamping frame 6 is fastened between the holders 4, 5 so that theclamping frame 6 can be altered in terms of its spatial orientation bythe movements of the holders 4, 5. To enable the separate verticaladjustment of the holders 4, 5 here, a longitudinal compensation meansis provided on one of the holders 4, 5 in a known manner.

A workpiece (not illustrated) can be fastened in a stationary manner onthe clamping frame 6 by holding elements, so that the workpiece can bespatially adjusted together with the clamping frame 6.

As a result of the individual vertical adjustability of the holders 4, 5and the rotatability about the workpiece axis A, an overalladjustability of the workpiece is provided in three directions or axesA, H1, H2 by means of the first frame 1.

A second frame 7 supports a tool pair 8 which comprises an upper tool 9and a lower tool 10. The tool pair 8 is formed overall as a combinedtool for drilling and riveting. A bore can firstly be incorporated inthe workpiece by means of the upper tool 9. A rivet is then insertedinto the bore and deformed by means of a common interaction of the uppertool 9 and the lower tool 10.

The upper tool 9 and the lower tool 10 are each movable in a transversedirection Q in the second frame 7 so that the setting of a machiningpoint can be adjusted substantially over a width of the second frame 7.

The second frame 7 has a supporting structure encompassing the tool pairin a closed manner, wherein the workpiece or the clamping frame 6reaches through an opening 11 surrounded by the supporting structure.The supporting structure is formed here as a rectangle comprising twohorizontal supports 12, 13 and two supports 14, 15 which areperpendicular thereto. Drives for the respective displacement of theupper tool 9 and lower tool 10 in the transverse direction Q are locatedin the horizontal supports 12, 13.

The upper tool 9 and the lower tool 10 are each adjustably displaceablerelative to the second frame 7 in a tool direction W which is at anangle to the transverse direction Q. For riveting, the upper tool 9 andthe lower tool 10 are aligned here with respect to the same axisextending in the tool direction W.

The second frame 7 is held on a swivel bearing 16 so that it can beswiveled about a swivel axis B. The swivel bearing 16 is formed as apivot bearing here so that the swivel axis B is a central axis ofrotation of the pivot bearing 16. The swivel movement of the secondframe 7 takes place accordingly together with the tool pair 8 held onthe second frame 7.

The swivel movement of the second frame 7 can be driven in acomputer-controlled manner via a rotary drive 17. Overall, all of themovements of the machining system which are described above and beloware driven in a computer-controlled manner.

The swivel bearing 16 is supported on a base frame 18 so that the secondframe 7 is held on the base frame 18 via the swivel bearing 16. Thesecond frame 7 is thus positioned high enough to enable it to swivelfreely.

The base frame 18 is seated on a guide 19 which comprises two rails andextends in a longitudinal direction L which is at an angle to thetransverse direction Q. The base frame is thus displaceable in adrivable manner on the guide 19 in the longitudinal direction L togetherwith the second frame 7.

By means of the second frame 7 and its holder on the displaceable baseframe 18, an adjustment of the machining point of the tool pair 8 canthus take place in three directions or axes, namely the transversedirection Q, the longitudinal direction L and the swivel axis B.

The extent of the clamping frame 6 is more than twice as long in thelongitudinal direction L than in the transverse direction Q. Theadjustment of an inclination of the clamping frame 6 about thetransverse direction Q correspondingly means a long travel of theholders 4, 5 in the vertical direction. This can be restricted by acorresponding adjustment of the swivel angle of the second frame 7.

Various embodiments function as follows:

A workpiece (not illustrated) is firstly fastened on the empty clampingframe 6. The workpiece can have a dome, which at least partly has acurvature about the transverse direction so that it is not planar in thelongitudinal direction. The position of the tool pair 8 is thencalibrated relative to the workpiece.

A first machining position is then approached and the workpiece ismachined in this position. To this end, a hole is drilled in theworkpiece by means of the upper tool 9 and a rivet is inserted. Therivet is then deformed or closed through cooperation between the uppertool 9 and the lower tool 10.

A second machining position is then approached, which is different fromthe first machining position at least in the longitudinal direction L.Owing to the non-planarity of the workpiece in the longitudinaldirection L, the second frame 7 here is swiveled about the swivel axis Bdepending on the surface of the workpiece. The tool direction W is thusnewly aligned in terms of its orientation with respect to the surface ofthe workpiece and spatially. In particular, it is generally desirableduring riveting that the tool direction W is aligned perpendicularly tothe surface of the workpiece at the machining point.

The workpiece is then machined in the second machining position andoptionally in further machining positions.

The movements of the clamping frame 6 and the workpiece and the toolpair 8 are also explained by the drawings FIG. 2 to FIG. 4. In FIG. 2,the same position of the machining system as in FIG. 1 is illustratedschematically.

In FIG. 3, the holders 4, 5 have been displaced differently along thevertical directions H1, H2 so that the clamping frame 6 and thereforethe workpiece axis A is tilted about the transverse direction Q. Thesecond frame 7 has been swiveled about the swivel axis B so that thetool direction W is in turn perpendicular to the clamping frame 6.

In FIG. 4, the clamping frame 6 has been additionally rotated about theworkpiece axis A, wherein the tool direction W is not perpendicular tothe clamping frame 6. This corresponds to a situation in which thesurface of the workpiece at the machining point has a correspondinginclination in relation to the clamping frame 6 so that the tooldirection W is adapted accordingly.

It should generally be noted that the mutual angular position of thedirections L, Q and H1 and H2 is potentially, but not necessarily, at aright angle. In such a case, the directions correspond to a stationaryCartesian coordinate system comprising an X-, Y- and Z-direction (seealso FIG. 2).

With regard to the tool direction W, this can be a direction which isnot fully adjustable in a simple embodiment. Therefore, for example, itis possible to specify only an optionally small travel of the upper tool9 for changing between two machining points. The lower tool here canhave no travel or only a small travel, wherein a vertical adjustment ofthe workpiece when changing the machining point takes place through thevertical directions H1, H2. In such an embodiment, the machining systemcomprises a total of six freely movable axes: H1, H2, A, Q, L and B.

In an embodiment, both the upper tool 9 and the lower tool 10 can bedisplaceable through a relatively large travel along the tool directionW so that the tool direction W is formed as a full adjustment axis foradjusting the machining point. This enables the travel in the verticaldirections H1 and H2 to be kept small. Depending on the length of theworkpiece or the clamping frame 6, it is thus possible to also keep theoverall height of the machining system low.

In a conceivable further development, when the adjustability of the toolpair 8 along the tool direction W is configured accordingly, it is alsopossible to dispense with the adjustment along one, in particular both,of the vertical directions H1, H2.

In an embodiment (not illustrated) it is finally the case that the firstframe 1 essentially only comprises a single positioning tower, whichholds the first frame 1 at the end. It is also conceivable that two ofsuch frames 1 are provided, which are each provided with a singlepositioning tower. It can then be the case that the two frames 1 eachspan a frame surface and that the frame surfaces are always in a commonplane.

1. A machining system for aircraft structural components, comprising: afirst frame for mounting a workpiece, and a second frame for mounting atool pair, wherein the tool pair comprises an upper tool and a lowertool cooperating therewith; wherein the workpiece is positioned betweenthe upper tool and the lower tool; wherein the second frame is formed tobe displaceable at least in a longitudinal direction with respect to abase; wherein the tool pair is held in the second frame such that it isdisplaceable in a transverse direction which is at an angle to thelongitudinal direction; and wherein the second frame is held on at leastone swivel bearing so that the second frame can be adjustably swiveledtogether with the tool pair about a swivel axis.
 2. The machining systemaccording to claim 1, wherein the tool pair comprises a riveting tool ora combined tool for drilling and riveting.
 3. The machining systemaccording to claim 1, wherein the second frame is held on a base framevia the swivel bearing, wherein the base frame is displaceable in thelongitudinal direction on a guide.
 4. The machining system according toclaim 1, wherein the second frame comprises a supporting structureencompassing the tool pair in a closed manner, wherein the workpiecereaches through an opening surrounded by the supporting structure. 5.The machining system according to claim 1, wherein at least one of thetwo, the upper tool or the lower tool, is adjustably displaceablerelative to the second frame in a tool direction which is at an angle tothe transverse direction.
 6. The machining system according to claim 1,wherein the first frame comprises two positioning towers which can bepositioned separately from one another in a stationary manner.
 7. Themachining system according to claim 1, wherein the first frame comprisesat least a first holder and a second holder, which are arranged at twoopposing end regions of the workpiece, wherein the first holder isadjustably displaceable in a vertical direction which is at an angle tothe longitudinal direction and the transverse direction.
 8. Themachining system according to claim 7, wherein the first holder isadjustably rotatable, wherein the workpiece is rotatable about aworkpiece axis through the rotation of the first holder.
 9. Themachining system according to claim 7, wherein the second holder is alsoadjustably displaceable in a vertical direction.
 10. The machiningsystem according to claim 7, wherein a clamping frame is connected tothe first holder and to the second holder, wherein the workpiece can bereleasably fastened to the clamping frame and the clamping frame ismovable by the holders.
 11. A method for machining an aircraftstructural component by a machining system according to claim 1,comprising: clamping a workpiece which has a non-planar surface in thelongitudinal direction in the first frame and calibrating a toolposition relative to the workpiece; approaching a first machiningposition and machining the workpiece; approaching a second machiningposition which is different at least in the longitudinal direction,wherein the second frame is swiveled about the swivel axis depending onthe surface of the workpiece in order to align the tool direction in itsorientation with respect to the surface of the workpiece; and machiningthe workpiece in the second machining position.
 12. The method accordingto claim 11, wherein the non-planar surface comprises a surface having adome.